1. Field of the Invention
This invention relates to a lawn tractor having a vehicle body, a center reel-type cutting unit, side reel-type cutting units arranged laterally of the center reel-type cutting unit with respect to a moving direction of the vehicle body, a first lift mechanism for vertically movably connecting the center reel-type cutting unit to the vehicle body, and second lift mechanisms for vertically movably connecting the side reel-type cutting units to the vehicle body.
2. Description of the Related Art
A riding lawn tractor having the above construction is disclosed in Japanese Patent Laying-Open Publication H5-328813, for example. This tractor includes a support frame projecting forward from the front of the vehicle body and pivotable about an axis extending transversely of the moving direction of the tractor body. The center reel-type cutting unit is connected to a free end of the support frame. Swing arms are arranged at opposite sides of an intermediate portion of the support frame to be pivotable about axes extending in the moving direction of the vehicle body. The side reel-type cutting units are connected to free ends of the right and left swing arms. The side cutting units are movable up and down with pivotal movement of the respective swing arms to vary spaces between reel blades and the ground.
In this type of lawn tractor, each reel-type cutting unit has ground-engaging wheels. With a support system allowing each cutting unit to move vertically as the ground-engaging wheels follow the ground, the cutting unit is movable up and down in response to unevenness of the ground. However, where, as in the conventional tractor, the right and left side reel-type cutting units are connected to the swing arms pivotable about the axes extending in the moving direction of the tractor body, the side cutting units, when raised and lowered, are displaceable transversely of the moving direction of the tractor body. As a result, cutting tracks also are displaceable transversely of the moving direction of the tractor body.
In the lawn tractor having a plurality of reel-type cutting units in juxtaposition, the cutting units describe cutting tracks transversely overlapping one another to leave no uncut patches. Where the cutting tracks are transversely displaceable with vertical movement of the cutting units as noted above, it is necessary for the cutting tracks to overlap by sufficient amounts to leave no uncut patches despite variations of the cutting tracks occurring during a cutting operation. This lowers the cutting efficiency of the respective cutting units.